Potentiometer



L B. LINDQUIST POTENTIOMETER June 23, 1970 Filed June 28, 1968 Wwf@ f MUnited States Patent O1 Patented June 23, 1970 3,517,368 POTENTIOMETERLarry B. Lindquist, Columbus, Nebr., assignor to Dale Electronics, Inc.,Columbus, Nebr., a corporation of Nebraska Filed June 28, 1968, Ser. No.741,095 Int. Cl. H01c 5/02 U.S. Cl. 338-180 3 Claims ABSTRACT OF THEDISCLOSURE A potentiometer including a leadscrew having an O-ringmounted in an annular groove formed in the head portion of theleadscrew. The groove positions the O-ring on the leadscrew and permitsthe leadscrew to be dropped into the potentiometer during the assemblyof the potentiometer. Cooperating case halves compress the O-ring aroundthe lead screw to seal the end of the potentiometer through which theleadscrew extends.

Conventional potentiometers include an elongated leadscrew which ismounted in the potentiometer by feeding the same through an O-ringbearing hole at one end thereof. The leadscrew is then held in place bya spring clip, roll pin, etc.

Therefore, it is a principal object of this invention to provide apotentiometer which is constructed to permit drop-in construction.

A further object of this invention is to provide a potentiometerincluding a leadscrew having an O-ring positioned in an annular grooveformed in the head portion of the leadscrew.

A further object of this invention is to provide a potentiometer havinga unique means for sealing the end of the potentiometer through whichthe head portion of the leadscrew extends.

A further object of this invention is to provide a potentiometer whichreduces the assembly time and the material costs.

A further object of this invention is to provide a potentiometer whereinan O-ring is compressed between cooperating case halves to seal one endof the potentiometer.

A further object of this invention is to provide a potentiometer whichprevents moisture failures of the potentiometer.

A further object of this invention is to provide a potentiometer whereinthe 360 degree bearing hole is eliminated.

A further object of this invention is to provide a potentiometer whichincludes a leadscrew having means thereon to position the same therebyeliminating the need for additional parts such as spring clips, rollpins, etc.

`A further object of this invention is to provide a potentiometer whichis economical of manufacture, durable in use and refined in appearance.

These and other objects will be apparent to those skilled in the art.

This invention consists in the construction, arrangements, andcombination of the various parts of the device, whereby the objectscontemplated are attained as hereinafter more fully set forth,specifically pointed out in the claims, and illustrated in theaccompanying drawings in which:

FIG. 1 is an exploded perspective view of a portion of thepotentiometer;

FIG. 2 is an enlarged sectional view of the potentiometer as seen alongline 2-2 of FIG. 1;

FIG. 3 is a sectional view as seen along lines 3-3 of FIG. 2;

lice

FIG. 4 is a fragmentary exploded perspective view of the potentiometerillustrating the cooperating case halves and their relationship to theO-ring on the leadscrew; and

FIG. 5 is a fragmentary end view of the potentiometer.

The potentiometer of this invention is generally designated by thereference numeral 10 and generally includes a case 12 and a lid 14. Case12 is constructed of suitable dielectric material such as plastic or thelike. Case 12 includes opposite ends 16 and 18, opposites sides 20 and22, bottom 24 and top 26. Case 12 also includes a compartment 28extending downwardly from the upper end thereof and which has aresistance coil 30 operatively mounted therein, the opposite ends ofwhich are connected to terminals 32 and 34 extending downwardly throughslots 36 and 38 respectively through the bottom of the case, asillustrated in the drawings. The numeral 40 generally designates anadjustment screw having an elongated threaded portion 42 and a headportion 44 mounted at one end thereof. A wiper arm assembly 46 isoperatively connected to the threaded portion 42 of screw 40 forlongitudinal movement therealong and operatively engages the resistancecoil 30. Wiper arm assembly 46 is operatively connected to a collectorbar means (not shown) which would be operatively connected to a terminal(not shown) extending downwardly through the bottom of the case.

Case 12 is provided with a recessed area generally indicated by thereference numeral 48 which is adapted to receive thelid 14 therein. Case12 is provided with an upstanding tab -50 having an opening 52 extendingdownwardly thereinto as best illustrated in FIG. 1. Opening 52 isgenerally semi-circular in shape but embraces more than 180 degrees orone-half of the threaded portion 42 of the screw 40 so that the threadedportion 42 may be snapped into the opening 52 thereby yieldablydetachably maintaining the same therein. Case 12 is also provided with ashoulder 54 which is adjacent the tab 50 and having an arcuate opening56 formed therein.

Head portion 44 of screw 40 includes a generally cylindrical shapedportion 58, an annular shoulder 60, and a peripheral groove 62. As seenin FIG. 2, the outer end of the head portion 44 is slotted at 64 toaccommodate a screwdriver to permit the rotation of the screw. Thenumeral 66 generally designates an O-ring which is mounted in the groove62 as best illustrated in FIG. 2. Case 12 is provided with asemi-circular opening 68 which receives the lower half of the O-ring 66therein. Case 12 is also provided with a groove 70 formed therein whichreceives the lower end of the shoulder 60 as best illustrated in FIG. 2.Cylindrical shaped portion 58 of head 44 is received by a generallysemi-circular shaped groove 72 which is spaced inwardly of an opening74. Opening 74 is generally semi-circular in shape but embraces slightlymore than 180 degrees or half of the cylindrical shaped portion 58 ofhead portion 44 so that the head portion 58 may be snapped into theopening 74 to yieldably maintain the leadscrew in the case 12.

Lid 14 includes a top 76, bottom 78, opposite ends and 82 and oppositesides 84 and 86. Lid 14 has a tab 88 extending downwardly therefrominwardly of end 80 which is provided with an arcuate opening 90 formedtherein. When the lid 14 is in place as illustrated in FIG. 2, opening90 partially receives the upper end of the threaded portion of theleadscrew while tab 88 is positioned above shoulder 54. The numeral 92designates a finger element extending outwardly from the opening 90which is positioned over the upper surface of the threaded portion 42 ofthe leadscrew 40. Lid 14 is also provided with a tab 94 extendingdownwardly therefrom inwardly of its end 82 which has an arcuate opening96 formed therein as illustrated in FIG. 1. When the lid 14 is in place,opening 96 receives the upper end of cylindrical shaped portion 58. Atab 98 is positioned at end 82 of lid 14 and extends downwardlytherefrom as best illustrated in FIG. 4. Tab 98 is provided with asemicircular opening 100 formed therein which is adapted to receive theupper half of the O-ring 66. As illustrated in FIG. 4, the tab 98 isreceived in the opening 102 formed in case 12. Tab 98 is also providedwith various weld beads 104 whilerthe underside of lid 14 is providedwith a weld bead 106 extending therearound. The potentiometer is easilyassembled by drop-in fabrication due to the open nature of the upper endof case 12. The resistance coil, terminal, wiper arm assembly andcollector bar means are easily inserted into the compartment 28 throughthe open upper end thereof. The screw 40 is dropped into the case 12 andsnapped into place in its openings 52 and 74. The O-ring 66 is mountedin the groove 62 prior to the screw being inserted into the case 12 andthe O-ring 66 and the shoulder 60 serve to position the screw, in thecase 12. The lid 14 is then installed on case 12 and the opening 100 andtab 98 and the opening 68 cooperate to compress the Oring 66 around thehead portion of the screw. The O-ring 66 is forced out from between thecooperating surfaces of the case 12 and lid 14 by the shape of the weldbead. The potentiometer may then be sealed by the use of ultrasonicWelding which causes the various weld beads to melt and further push theO-ring into the head portion of the screw. The process and the designjust described prevents pinching of the O-ring between -the cooperatingsurfaces of the case 12 and lid 14 which could cause damage to theO-ring and which could cause moisture failure of the potentiometer.

Thus it can be seen that the drop-in screw reduces labor costs becauseit does not need to be fed through an O-ring bearing hole as must bedone in conventional potentiometers. Additionally, the design describedherein eliminates the need for a spring clip, roll pin, etc. to maintainthe screw in place in the case. The absence of such a spring clip or thelike also reduces the total cost of the unit. The lack of the O-ringbearing hole in the case reduces the cost of the part because of fastercycling time since the mold does not need to contain core pins for suchan opening.

Thus it can be seen that a unique means has been provided for sealingone end of a potentiometer through the 'use of cooperating case halveswhich compress the O-ring around the head portion of the lead screw.Thus it can be seen that the potentiometer accomplishes at least all ofits stated objectives.

Some changes may be made in the construction and arrangement of mypotentiometer without departing from the real spirit and purpose of myinvention, and it is my intention to cover by my claims, any modifiedforms of structure or use of mechanical equivalents which may bereasonably included within their scope.

I claim:

1. In a potentiometer,

a case having upper and lower ends, opposite ends and opposite sides,said upper end being open, said case having a compartment formed thereinextending downwardly thereinto from its open upper end,

an elongated resistance means in said compartment operatively connectedto a first and second terminal means,

an adjustment screw rotatably mounted in said case and having a headportion mounted at one end thereof, said screw having a threadedportion, said head portion being rotatably mounted in one of said endsof said case,

a Wiper arm assembly operatively mounted on said screw in saidcompartment for longitudinal movement therealong, said wiper armoperatively engaging said resistance element and being operativelyconnected to a third terminal means,

said screw head portion having a peripheral slot extending therearound,

an O-ring mounted in said slot,

and a lid mounted on said case sealably closing the upper end of saidcompartment and engaging said O-ring to compress the same between saidvlid and said case to seal the one end of the potentiometer through whichsaid screw head portion extends,

said case having adjustment screw supporting areas at each of its endsadapted to support said adjustment screw in said case,

each of said supporting areas having an opening formed therein extendingdownwardly thereinto adapted to rotatably receive opposite ends of saidadjustment screw, said openings having open upper ends to permit saidadjustment screw to be placed in said case downwardly through the openupper end of said case and downwardly into said openings in saidsupporting areas,

said openings being semi-circular in shape and rotatably embracing saidadjustment screw greater than degrees but less than 360 degrees toyieldably detachably maintain said screw in said case.

2. The potentiometer of claim 1 wherein said case has a semi-circularopening at its said one end which receives a portion of said O-ring,said lid having a tab extending downwardly from one end thereof, saidtab having a semi-circular opening formed therein which receives aportion of said O-ring.

3. The potentiometer of claim 1 wherein one of said openings receivesone end of the threaded portion of said adjustment screw and the otherof said openings receives said screw head portion.

References Cited UNITED STATES PATENTS 2,908,881 10/1959 Pitzer 338-164XR 3,134,955 5/1964 Hardison et al. 338-180 3,238,488 3/1966 Langenbachet al. 338-180 3,341,799 9/ 1967 Van Ben Thuysen et al.

338-164 XR 3,399,369 8/1968 Soulakis 338-180 3,414,862 12/1968 Ginsberg338-180 THOMAS J. KOZMA, Primary Examiner U.S. Cl. X.R.

